A computer system frequently needs data and/or services from another computer system. For example, a bank customer may request to see his current bank account information on his home computer system, which obtains the requested information from a computer system maintained by and located at the bank. In such arrangements, the computer system requesting the data and/or service is referred to and known as the “client” system, and the computer system servicing the request is referred to and known as the “server” system.
Many entities, for various reasons, situate groups of servers and related electronic equipment in “server rooms” or “data centers.” Within a server room, several servers may be positioned vertically atop one another (with spacing) using a “rack.” Racks of servers, memory units, power supplies, computers, etc. (hereinafter generally referred to as “electronic equipment”) are often housed or enclosed in housings known as “cabinets” that provide protection from environmental variables such as, for example, light and dust. Cabinets may have front and back doors so as to allow for the servicing and changing of cabinet components. Moreover, cabinets reduce or prevent electromagnetic interference that might otherwise exist between, for example, different servers.
An important issue regarding server rooms and server operation involves temperature. As those skilled in the art will note, computer operation results in heat dissipation. In a server room, many electronic components are be operating at the same time, and thus, without adequate cooling, the components and related electronic equipment in the server room may be damaged or operate incorrectly as a result of high temperatures.
One cooling technique cools servers and related electronic equipment using air supplied from within the server room. FIG. 1 shows such a server room 110. The server room 110 has two cabinets 112, 114, each of which houses servers and/or related electronic equipment (not shown). Cold air is introduced into the server room 110 using a plenum 116 of cold air supplied by an air conditioning unit (not shown). The cold air from the plenum 116 is directed to the front of each cabinet 112, 114. Cold air entering the front of each cabinet 112, 114 flows through the cabinets 112, 114 and is heated by the heat dissipation of the electronic equipment housed in the cabinets 112, 114. Consequently, hot air exits from the rear of each cabinet 112, 114 and returns to the server room 110. The hot air rises and enters a cooling coil 118, which uses water or a refrigerant supplied by a chiller unit 120 to cool the hot air and return cold air back to the server room 110. This returned cold air is directed to the front of each cabinet 112, 114.
As servers and related electronic equipment become more powerful, heat dissipation increases. In other words, as servers and related electronic equipment continue to improve in terms of density, computing speed, and performance, more energy is released, thereby resulting in increased heat dissipation. Using only an air cooling technique to cool a server room having such increased heat dissipation requires the consideration of several issues. For example, air cooling such a server room might require an air plenum below the floor of the server room that is significantly wider than one used for a server room not having increased heat dissipation. Further, the mixing of cold air and hot air in the server room might be of more significant concern than in a server room not having increased heat dissipation. Further, the increased volume of air flow that would be required to cool the server room might render the server room uncomfortable for operators and technicians in the server room.
A technique that may be used to somewhat address the concerns associated with using only air cooling to cool high heat dissipation server rooms involves the use of a liquid coolant. Liquid cooling may be used in combination with a front-to-back air cooling technique, such as that described above with reference to FIG. 1. FIG. 2 shows such a technique. Particularly, FIG. 2 shows a side view of a cabinet 204. An air-liquid heat exchanger 202 is placed at the bottom of the cabinet 204 underneath electronic equipment (e.g., servers) 206. The hot air exiting from the rear of the electronic equipment is captured by a back door 208 of the cabinet 204 with fans (not shown) and is directed down along the back door 204 to the air-liquid heat exchanger 202. The air-liquid heat exchanger 202 cools the hot air, and the resulting cold air is directed up the front of the cabinet 204 between a front door 210 of the cabinet 204 and the electronic equipment 206 to be cooled. The air re-circulates within the cabinet 204 as the front door 210 and back door 208 of the cabinet 204 are closed. Those skilled in the art will note that the front and rear surfaces of the electronic equipment 206 represent space for connectors for the electronic equipment 206, and thus, front-to-back air cooling may limit such use of the front and rear surfaces of the electronic equipment 206.
Another technique used in conjunction with air cooling is cold plate cooling. Electronic equipment may be directly cooled using a cold plate. In other words, electronic equipment is cooled by contacting a cold plate device. Typical designs for cold plates include tubed cold plates and gun-drilled cold plates. In a tubed cold plate design, metallic tubes are embedded in a planar metal base. The tubes are usually formed from copper or stainless steel, while the cold plate is typically formed from copper or aluminum. In a gun-drilled cold plate design, holes are drilled directly into an aluminum or copper plate. These tubes or holes allow for the passage of a cooling fluid, which maintains the cold plate at a temperature useful for cooling electronic equipment attached to the cold plate. Cold plates may be configured to be compatible with many fluids and provide adequate bulk heat removal.